In recent years, the application range of magnetic recording devices, such as magnetic disk devices, flexible disk devices, and magnetic tape devices, has been significantly widened, and the importance thereof has increased. In addition, a technique for improving the surface recording density of magnetic recording media used for the devices has been developed. In particular, the introduction of an MR head and a PRML technique significantly increases the surface recording density. In recent years, for example, a GMR head and a TMR head have been developed to increase the surface recording density at an increasing rate of about 100% per year. In addition, there is a demand for further increasing the surface recording density of the magnetic recording medium. Therefore, in order to meet the demand, it is necessary to improve the coercive force of a magnetic recording layer, increase a signal-to-noise ratio (SNR), and increase the resolution thereof. In addition, there is an attempt to improve a linear surface recording density and a track density, thereby increasing the surface recording density.
In recent years, the track density of the magnetic recording device has reached 110 kTPI. However, when the track density increases, magnetic recording information items in adjacent tracks interfere with each other, and a magnetization transition area at the boundary therebetween serves as a noise source, which may decrease the SNR. The lowering of the SNR causes a reduction in bit error rate (bit error rate), which makes it difficult to increase the surface recording density.
In order to increase a surface surface recording density, it is necessary to greatly reduce the size of each recording bit on the magnetic recording medium and ensure a large amount of saturated magnetization and a large magnetic film thickness for each recording bit. However, when the size of the recording bit is greatly reduced, a minimum magnetization volume per bit is reduced, which may cause recorded data to be erased due to magnetization reversal caused by heat fluctuation.
In order to decrease the distance between tracks, the magnetic recording device requires a high-precision track servo technique and generally uses a method of performing recording with a large width and reproducing with a width that is smaller than that during recording in order to minimize the influence of adjacent tracks. The method can minimize the influence between adjacent tracks, but it is difficult to obtain a sufficient reproduction output, which makes it difficult to ensure a sufficiently high SNR.
As a method of solving the problem of the heat fluctuation and ensuring a sufficient SNR or a sufficient output, the following has been attempted: a technique for forming an uneven pattern on the surface of a recording medium along tracks or forming a non-magnetic portion between adjacent tracks to physically separate the tracks, thereby increasing track density, which is referred to as a discrete track method.
As an example of a discrete track magnetic recording medium, a magnetic recording medium is known in which a magnetic recording layer is formed on a non-magnetic substrate having an uneven pattern formed thereon to form magnetic recording tracks physically separated from each other and a servo signal pattern (for example, see Patent Document 1). In the magnetic recording medium, a ferromagnetic layer is formed on the surface of the substrate having a plurality of uneven portions formed thereon with a soft magnetic layer interposed therebetween, and a protective film is formed on the ferromagnetic layer. In the magnetic recording medium, a magnetic recording region is formed in a convex region so as to be magnetically isolated therefrom.
According to the magnetic recording medium, it is possible to prevent the occurrence of a magnetic domain wall in the soft magnetic layer. Therefore, the magnetic recording medium is hardly affected by the thermal fluctuation, and there is no interface between adjacent signals. As a result, it is possible to form a high-density magnetic recording medium with little noise.
Examples of the discrete track method include a method of forming a magnetic recording medium having a multi-layer structure and then forming tracks, and a method of forming an uneven pattern on the surface of a substrate directly or with a thin film for forming tracks interposed therebetween and then forming a thin film of a magnetic recording medium (for example, see Patent Documents 2 and 3). The latter is referred to as a pre-emboss method or a substrate processing type. In the pre-emboss method, a physical process is completely performed on the surface of a medium before the medium is formed. Therefore, it is possible to simplify a manufacturing process and prevent a medium from being contaminated during the manufacturing process. However, since the uneven pattern formed on the substrate is transferred to the formed film, the floating posture and the floating height of a recording/reproducing head that records or reproduces data while floating from the medium become unstable.
Meanwhile, in recent years, there is an increasing demand for improving the operating speed of a semiconductor device and reducing the power consumption thereof, and a technique for incorporating a system LSI into the semiconductor device has been demanded. In order to meet the demands, with the development of a lithography technique, which is the core technology of a semiconductor device process, the cost of an apparatus has increased.
In recent years, an exposure lithography technique has been changed from a KrF laser lithography technique having a minimum line width of 130 nm to an ArF laser lithography technique having a resolution that is higher than that of the KrF laser lithography technique.
The minimum line width of the ArF laser semiconductor technique in the mass production stage is 100 nm. However, lithography devices having minimum line widths of 90 nm, 65 nm, and 45 nm were manufactured in 2003, 2005, and 2007.
In order to further reduce the minimum line width, the following techniques are expected: a F2 laser (F2 excimer laser) lithography technique; an extreme ultraviolet lithography (EUVL) technique; an electron beam projection lithography (EPL) technique; and an X-ray lithography technique. These lithography techniques succeed in manufacturing a pattern in the range of 40 nm to 70 nm.
However, with the development of fine pattern lithography, the cost of the exposure apparatus has exponentially increased, and the cost of a mask for obtaining the same resolution as the light wavelength used has suddenly increased. Therefore, nanoimprint lithography has drawn attention as an inexpensive processing technique having a resolution of about 10 nm (see Patent Document 4).    [Patent Document 1] JP-A-2004-164692    [Patent Document 2] JP-A-2004-178793    [Patent Document 3] JP-A-2004-178794    [Patent Document 4] JP-A-2004-504718